Sand blowing apparatus



April 30, 1957 H. .1. B. HERBRUGGEN 2,790,215

SAND BLOWING APPARATUS Filed July 26, 1952 4; 92 ATTORNEYS INVENTOR 7 United States Patent SAND BLOWING APPARATUS Heinrich J. B. Herbruggen, Cleveland, Ohio, assignor to The Federal Foundry Supply Co., Cleveland, Ohio, a corporation of Ohio Application July 26, 1952, Serial No. 301,107

4 Claims. (Cl. 22-10) This invention relates to a sand blowing apparatus and control system and more particularly to the regulation of fluid pressure in the apparatus.

In the blowing of molds, flasks and cores, the conventional apparatus normally utilizes fluid pressure to aid in conveying and propelling sand from a transfer chamber into a sand receptacle. In practice, the sand receptacle may be provided with vents to the atmosphere to allow the fluid pressure to escape from the receptacle during the delivery of sand. In spite of generous venting in a conventional apparatus, the pressure is likely to build up in the receptacle to an undesirable value which causes damage to the receptacle, particularly in the case of frail wooden core boxes and the like.

Accordingly, it is an object of this invention to limit the pressure obtainable in a sand receptacle during the blowing operation to a safe predetermined value.

Briefly, in accordance with this invention there is provided a sand blowing apparatus having a sand transfer chamber with a fluid pressure inlet and exhaust. The chamber has a blow plate with a sand discharge opening adapted to communicate with a sand receptacle in sand blowing relation. A vent plate is provided between the blow plate and sand receptacle to enable the release of fluid pressure from the receptacle during the blowing operation. The sand blowing cycle may be initiated and terminated by hand operation or by automatically controlling the fluid pressure inlet and exhaust to the chamber. Electromagnetically controlled valves are provided for the inlet and exhaust and a timer periodically interrupts the control circuit to the inlet valve to admit fluid pressure to the chamber in pulsations at a predetermined periodic rate which does not allow the pressure to build up to an undesirable value in the sand tacle.

In the drawings, Fig. 1 is a vertical view in partial section of a core blowing apparatus and control system emrecepbodying the regulated fluid pressure supply to the transfer chamber;

Fig. 2 is a schematic diagram of an electromagnetic control circuit for the apparatus of Fig. 1.

The sand blowing apparatus of Fig. 1 embodies an enclosed vertical frame having a base 10 and a vertically spaced crosshead 11 interconnected with spaced vertical columns 12 and 13 to form a rigid load-distributing supporting structure. Within the top portion of the enclosed frame is a sand transfer chamber 14 which is pivotally supported at the ends of arms 15 and 16 extending from pivotal connections at the column 12 to enable limited vertical movement of the transfer chamber within the frame. The frame also carries at the column 12 a sand hopper 18 external to the frame and having a discharge opening 19 with a pivoted gate closure 20 and a loosely supported scraper ring 21. The supporting arms 15 and 16 of the transfer chamber 14 are preferably pivoted to a journal 17 which is rotatably mounted on the column 12 to enable the sand transfer chamber 14 to be swung about the column into filling po- Patented Apr. 30, 1957 'ice.

of a lift piston 23 is operatively disposed within the lower portion of the closed frame so that when fluid pressure is applied to the lift piston cylinder 22 the sand receptacle 25 is lifted upwardly against the sand transfer chamber 14 and then the entire assembly is positioned and clamped in core blowing relation against the frame crosshead 11. In this position the filling opening of the sand transfer chamber communicates through a filter 27 with an exhaust space 28 in the crosshead 11 and the exhaust space is controlled by a spring-loaded fluid pressure operated exhaust valve 29.

The crosshead 11 also has a valve controlled fluid pressure inlet 33 which communicates with an air jacket within the sand transfer chamber in sand blowing position.

In the preferred embodiment shown in Fig. 1, the sand transfer chamber 14 has an inner perforated partition 30 forming a sand room and carries a removable blow plate enclosure 38 at its base with a sand discharge opening 34. An agitator is rotatably supported within the sand room from a driving gear ring 36 at the top of the transfer chamber, and a spur gear 37 for driving-the agitator ring 36 is operatively disposed outside the sand room and within the air jacket of the chamber for protection against sand and dirt. The blow plate 38 at the bottom of the transfer chamber 14 carries a vent plate 40 with openings communicating between the sand receptacle 25 and the atmosphere for venting the receptacle.

In Fig. 1, the sand blowing cycle is initiated by positioning the valves 50 and 51 which normally isolate the fluid pressure supply from the sand receptacle lift mechanism and the fluid pressure inlet respectively. When these valves are opened, fluid pressure is applied from valve 51 to conduit 55 to the cross-head 11 and then through branches 57 and 59 to counteract the loading springs 53 and 52 of the inlet and exhaust valves 44 and 29 respectively. Thus, the fluid pressure inlet 33 is opened and the exhaust 47 from the sand transfer chamber is closed. The valve 50 is first positioned to supply fluid pressure to the lift cylinder 22 to position and clamp the sand receptacle 25 and transfer chamber 14 in sand blowing relation against the crosshead 11 within the closed frame. Then fluid pressure passes through the inlet 33 and the air jacket and through the perforated partition 30 into the sand room and outwardly as a propellent with the sand through the discharge opening 34 in the blow plate 38 to fill and compact the sand Within the receptacle 25. The fluid pressure within the receptacle will ultimately vent through the vent plate 40 to the atmosphere.

In the preferred embodiment of the apparatus shown in Fig. 1, the fluid pressure outlet from valve 50 or the supply conduit 56 leading from the valve 50 to the lift piston cylinder 22 is restricted in size to supply a restricted flow of fluid pressure to limit the rate of lifting travel of the lift piston 23 within the cylinder to a predetermined safe rate that will prevent damage to the receptacle 25 when engaging the vent plate 40 on the transfer chamber 14. The lift piston cylinder 22 also communicates with the main supply line 45 through a valve 60 which is biased closed by a spring 61 against the fluid pressure in a branch line 62 of the conduit 56. The branch conduit 62 is normally isolated from the conduit 56 by a spring loaded valve 65 which responds to pressure developed in the branch conduit 63 and the lift piston cylinder 22. When the lift piston 23 reaches the limit of its travel consequent upon the assembly of the receptacle 25 and transfer chamber 14 engaging the crosshead 11 of the frame, a pressure is developed in the lift piston cylinder 22 which is suflicient to overcome the spring loading of the valve and establish communication through thebranch conduit 62-between the valve 60 and the conduit 56. The pressure thus admitted to the conduit 62 is sufiicient to overcome the spring loading on the-valve 60- and opens the main fluid'supply line 45 to the lift piston cylinder '22 to apply-an increased-clampingforee to the piston 23, to maintain the receptacle 25 and transfer chamber 14 assembled in .core'blowin g re-v lation against the crosshead 11 within the frame.

A difierential exhaust valve 68 is provided in a branch line 59-from the conduit 56 to the lift piston cylinder 22. Thevalve 68 will maintain the exhaust vent 70 closed untilsuch time as the fluid pressure is removed from the conduit 56 and the pressure within thelift'cylinder 22 positions the valve 68' to i open the exhaust. ent 70; I The positioning of the valve members 50 and 51 is preferably automatically 7 controlled by electromagnetic solenoids 80 and 81 respectively'whichare connected in the energizing circuit shown in Fig. 2 of the drawings. In the preferred embodiment, the operation of the sand blowing cycle is initiated by momentarily compressing a starting contact 82 which energizes a solenoid 83 to position and close the contacts 84 and energize the branch circuits containing the valve operating solenoids 80and 81. A suitable spring bias roll latch 85 secures and holds the contacts 84 in closed position until such time as the latch is removed by energizing the solenoid 86 in a manner that will be hereinafter more fully described.

It Will be seen that the closing of the contacts 84 energizes the solenoid 80 to open the valve 50 and supply a restricted flow of fluid pressure to the lift piston 22 as previously described. The solenoid 81 controlling the valve 51 will not be energized however until the contactor 87 is closed. This contactor is: actuated by a lever arm 88 carried by a differential valve 90 which is normally positioned in the open position under the main fluid pressure supply until such time as the pressure developed in the lift piston cylinder 22 is sufficiently great to counterbalance the main fluid pressuresupply and position valve 90 to close the contactor 87. This will not take place until the sand receptacle 25 and transfer chamber 14 are assembled in sand blowing relation against the crosshead 11 within the frame. Then the valve 51 is positioned to supply fluid pressure to open the chamber inlet valve 44 and to close the chamber exhaust valve 29. The solenoid 81 may also be provided with a normally open series contactor 103 which is not closed until the core box 25 engages the vent plate 49 of the sand transfer, Chamber 14, thereby providing a safety switch which will prevent the admission of fluid pressure to the chamber14 until after the receptacle 25 is positioned in sand blowing relation against thevent plate 40.

Another set of contacts 100 is connected in series with the solenoid 81 and has a contact arm that is mechanically or electrically coupled to a suitable timing mechanism which is preferably shown as an electrical timer 101 in the circuit of Fig. 2. The timer 101 illustrated in Fig. 2 is in the form of a synchronous motor driven cam which periodically engages the contact arm to close the. circuit to the solenoid 81 for the admission of fluid pressure to the chamber 14. The timer cam is designed to allow the contacts 188 to remain closed for a predetermined period of time which will allow the pressure to build up sufliciently in the chamber and receptacle to maintain proper blowing actionand then opens the contacts 198 to deenergize solenoid 81 and remove the pressure from the chamber inlet 33 to thereby limit the pressure within the receptacle 25 and prevent damage from excess pressure. This operation is periodically performed as the motor'driven timer cam rotates on its shaft so that the fluid pressure is admitted to the transfer chamber 14 in pulsations at a predetermined periodic rate. The rate of speed at which the cam rotates and thecam surface may r 2,790,215. i F -f each be adjusted in accordance with the requirements of the blowing apparatusand type of sand receptacle used. Thus, the maximum pressure attainable in a sand receptacle may be adjustably controlled in accordance with the type of sand receptacle used as well as to accommodate difierent sources of fluid pressure and different venting arrangements.

In Fig. 2,. the cam Operation positions the valve 51 to periodically close the inlet 33 and open the exhaust 28 so that thepr ssureis reduced. after each pulse admission. of fluid pressure to. the transferchamber 14. This operation could be modified to maintain the exhaust closed throughout the sand blowing cycleand pulse only the admission of fluid pressure to the transfer chamber 14 by incorporating another valve in the chamber inlet 33 and controlling the positioning of the valve with the timer. An alternative operation is shown and described in my co-pending applicationiSer. No. 286,774 filed May 8; 1952, and entitled Control System for Core Blowing Apparatus'where the fluid pressure line 59 for position ing the exhaust valve 29 is provided with a one way check valve and the'exha'ust valve chamber within the crosshead 11 has an exhaust vent controlled by a solenoid positioned valve which is energized to open the vent when a cycle. terminating contactor 96-is closed.

In any event, the fluid pressure to the receptacle 25 is regulated to limit the unit pressure within the receptacle to a predetermined safe value.

The agitator 35 within the sand room is preferably driven by an electrical motor M which has an energizing winding 92 connected in parallel with the solenoids and 81 in the circuit of Fig. 2. The motor M is not energized until the normally open contacts 93 in series with the energizing winding 92 are closed. These contacts 93 are closed by a switch arm 94 that is carried by a fluid pressure operated valve 95 which is coupled through the branch conduit 63 to the pressure developed in the lift piston cylinder 22. Thus the contacts 93 are not closed and the agitator motor M is not energized until the sand receptacle 25,- and transfer chamber 14 are secure and assembled in clamped sand blowing relation against the crosshead 11 within the frame.

In the control circuit'of Fig. 2, the sand blowing cycle is automatically terminated when the sand receptacle 25 is, filled with sand. This is accomplished by providing normallyopen contacts 96 in series with the latch solenoid 6 so thatwhen the ont ct 96 are ose he s len id. 8 is energized and the latch removed from the contaet arm of contacts 84 to open the energizing circuit to the solenoid Silandfil and to the agitator motor winding 92. The contacts are preferably in the form of a mercury switch which is supported on a scale arm pivoted intermediate its ends and having fluid pressure valvehchamhers 1,11 .a nd 112 formed: rfispcctively in each; end. Fluid pressure is applied to the valve chambers and each end of the scale arm 110 from orifices in conduitsv 113, and 114 leading from the air jacket of the transfer chamber 14. As long, as the sand receptacle 25 is not filled with sand, fluid. pressure admitted into the transfer chamber 14 flows from the inlet 33. through the air jacket andthrough the discharge, opening 34 into the sand receptacle 25 creating a differential of pressure within the transfer chamber 14.- The scale arm 119 is designed so that as long as a differential'of pressure exists within the transfer chamber 14 the mercury switch 96 remains open. As soon as the receptacle 25 is filled with sand, however, the pressure within the transfer chamber 14 is equalized to unbalance the scale arm 110 and close the mercury switch 95, which in turn energizes the solenoid 86 and unlatches the contacts 84 to open the energizing circuit to the solenoids 80, 81 andthe agitator winding 92and terminates the sand blowing cycle.

Thus the sa d bl in app a u vis pm ed'with a continued flu d press re and elect cal on r l system which automatically initiates and terminates the sand blowing cycle While performing the sand receptacle positioning and blowing operations in proper sequence during the cycle. The apparatus and system also limits the positioning rate of travel of the sand receptacle and the pressure in the receptacle to predetermined safe values during the blowing cycle, thereby preventing damage to the receptacle and the apparatus and insuring against the escape of sand from between the transfer chamber and sand receptacle during the sand blowing cycle. As a result, frail sand receptacles such as core boxes made of wood and the like which heretofore have been necessarily made by hand may now be processed in an automatically controlled sand blowing apparatus without fear of destruction or damage. The control of the maximum pressure attainable in the sand receptacle also eliminates the need for insuring that the top and bottom of the sand receptacle are absolutely parallel in order to prevent sand from escaping under pressure between the blowhead and the mating side of the sand receptacle as is the case in a conventional blowing apparatus.

I have shown and described what I consider to be the preferred embodiment of my invention, along with similar modified forms and suggestions and, it will be obvious to those skilled in the art that, similar changes and modifications may be made without departing from the scope of my invention as described by the appended claims.

I claim:

1. In a sand blowing apparatus having a sand transfer chamber with a discharge opening in communication with a sand receptacle, said chamber having a fluid pressure inlet, a valve in said inlet, electromagnetic means for positioning said valve to open and close the chamber inlet, means for energizing said electromagnetic means, and other means automatically operative during the blowing cycle to periodically activate said energizing means at predetermined intervals to supply pulsations of fluid under pressure to the transfer chamber.

2. In a sand blowing apparatus having a transfer chamber with a discharge opening in communication with a sand receptacle, an inlet in said chamber for admitting fluid under pressure thereto, a valve in said inlet, electromagnetic means for positioning said valve to open and close the chamber inlet, an electrical circuit including a switch for energizing said electromagnetic means, a timer mechanism coacting with said switch to periodically open and close the circuit at predetermined intervals to supply pulsations of fluid under pressure to the transfer chamber.

3. In a sand blowing apparatus having a sand transfer chamber with a discharge opening adapted to communicate with a sand receptacle, a fluid pressure inlet for the transfer chamber, electromagnetically controlled means for supplying fluid under pressure to the chamber inlet, an electrical circuit including a switch for energizing said electromagnetic means, a lift mechanism for positioning and clamping the sand receptacle and transfer chamber in sand blowing relation, means coacting with said lift consequent upon the receptacle and transfer chamber being positioned in sand blowing relation to close said switch and supply fluid under pressure to the chamber inlet, said circuit including also a normally closed switch, and a timer mechanism coacting therewith to periodically open and close said normally closed switch for predetermined intervals to supply pulsations of fluid under pressure to the transfer chamber.

4. In a sand blowing apparatus having a sand transfer chamber with a discharge opening adapted to communicate with a sand receptacle, a fluid pressure inlet for the transfer chamber, electromagnetically controlled means for supplying fluid under pressure to the chamber inlet, an electrical circuit including a switch for connecting said electromagnetically controlled means to a source of electrical energy, a lift mechanism movable towards and away from the transfer chamber for positioning and clamping the sand receptacle and transfer chamber in sand blowing relation, means coacting with said lift mechanism when moved to position the receptacle in sand blowing relation against the transfer chamber to close said switch and thereby to initiate the supply of fluid under pressure to the chamber inlet, said circuit including also a normally closed switch, a timer mechanism coacting therewith to periodically open and close said normally closed switch to intermittently interrupt the supply of fluid under pressure to the transfer chamber, and other means operative in response to the attainment of a predetermined unit pressure differential in the transfer chamber consequent upon said receptacle being filled with sand to disconnect the circuit and the electromagnetically controlled means from the source of electrical energy and to thereby automatically remove the fluid pressure supply from the chamber inlet to terminate the sand blowing cycle.

References Cited in the file of this patent UNITED STATES PATENTS 1,030,326 Peterson June 25, 1912 1,086,824 Hewlett et a1. Feb. 10, 1914 1,563,156 Barman Nov. 24, 1925 1,595,600 Demmler Aug. 10, 1926 2,437,831 Moore Mar. 16, 1948 2,553,946 Herbruggen May 22, 1951 

